1. Field of the Invention
The present invention relates to lithography, and more particularly, to maskless lithography involving one or more pattern generating devices.
2. Background of Invention
Lithography systems are used to print features in a variety of manufacturing applications. Photolithography systems use a mask or reticle to expose features onto an object. In semiconductor manufacturing, for example, a reticle is exposed by an exposure beam. An optical system then projects a reduced image of the reticle onto a silicon wafer. In this way, circuit features can be printed on a semiconductor substrate.
Maskless lithography systems have been developed that do not require use of a mask or reticle. Current maskless lithography systems project a pattern to be printed onto a moving object. For example, a pattern of circuit features can be projected onto a moving wafer or flat panel display. In one example, a silicon wafer can be coated with a photoresist. The pattern is projected on the wafer using one or more pattern generating devices, such as one or more spatial light modulators (SLM). Types of SLMs can include, for example, digital micromirror devices (DMD), transmissive liquid crystal light valves (LCLV), and grating light valves (GLV).
In maskless lithography involving multiple pattern generating devices, such as multi-SLM maskless lithography, multiple SLMs are typically used in a flat plan to generate a pattern onto a work surface, such as a wafer or flat panel display. Relatively large gaps can exist between SLMs in a multi-SLM maskless lithography system. These gaps lead to a large amount of scattered light reaching a wafer in areas between the active portions of the SLMs, which should remain dark. Improper dose control and loss of contrast in the wafer imaging, for example, can result that leads to degraded imaging and reduced circuit performance for the device being produced.
What are needed are systems and methods for minimizing scattered light in multi-pattern generating device maskless lithography systems.